Semiconductor device and method for manufacturing semiconductor device

ABSTRACT

A semiconductor device includes: a metal sheet; an insulating pattern provided on the metal sheet; a power circuit pattern and a signal circuit pattern that are provided on the insulating pattern; a power semiconductor chip mounted on the power circuit pattern; and a control semiconductor chip that is mounted on the signal circuit pattern and controls the power semiconductor chip. The power semiconductor chip is bonded to the power circuit pattern with a first die bonding material comprised of copper, and the control semiconductor chip is bonded to the signal circuit pattern with a second die bonding material.

BACKGROUND OF THE INVENTION Field of the Invention

The present disclosure relates to a semiconductor device and a method for manufacturing the semiconductor device.

Description of the Background Art

Conventionally, a semiconductor device in which a power semiconductor chip and a control semiconductor chip for controlling the power semiconductor chip are integrated into one module has been commercialized. Such a semiconductor device is required to be further miniaturized.

For example, Japanese Patent Application Laid-Open No. 2013-149779 discloses a semiconductor device in which a circuit pattern to which a power semiconductor chip and a control semiconductor chip are bonded is configured with a thin metal sheet such as a lead frame. By reducing the thickness of the circuit pattern, it is possible to achieve miniaturization of the semiconductor device.

However, in the semiconductor device described in Japanese Patent Application Laid-Open No. 2013-149779, since the circuit pattern is composed of a thin metal sheet such as a lead frame, the thermal conductivity of the circuit pattern is lowered. As a result, there is a problem that the heat dissipation for the power semiconductor chip is deteriorated.

SUMMARY

An object of the present disclosure is to provide a technique capable of ensuring heat dissipation for a power semiconductor chip and achieving miniaturization of a semiconductor device.

A semiconductor device according to the present disclosure includes: a metal sheet; an insulating pattern; a circuit pattern; a power semiconductor chip; and a control semiconductor chip. The insulating pattern is provided on the metal sheet. The circuit pattern is provided on the insulating pattern. The power semiconductor chip is mounted on the circuit pattern. The control semiconductor chip is mounted on the circuit pattern and controls the power semiconductor chip. The power semiconductor chip is bonded to the circuit pattern with a first die bonding material comprised of copper. The control semiconductor chip is bonded to the circuit pattern by a second die bonding material.

Since the first die bonding material comprised of copper is used to bond the power semiconductor chip to the circuit pattern, the heat dissipation for the power semiconductor chip is improved as compared with a conventional case where solder is used. As a result, heat dissipation for the power semiconductor chip can be ensured even when the circuit pattern is thinned. As a result, it is possible to secure heat dissipation for the power semiconductor chip and to achieve miniaturization of the semiconductor device.

These and other objects, features, aspects and advantages of the present disclosure will become more apparent from the following detailed description of the present disclosure when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view illustrating a structure of a semiconductor device according to a first preferred embodiment;

FIG. 2 is a cross-sectional view taken along line A-A of FIG. 1;

FIG. 3 is a circuit diagram of the semiconductor device according to the first preferred embodiment;

FIGS. 4A to 4C are cross-sectional views each illustrating a method for manufacturing the semiconductor device according to the first preferred embodiment;

FIGS. 5A to 5F are cross-sectional views each illustrating a method for manufacturing a semiconductor device according to a first variation of the first preferred embodiment.

FIGS. 6A to 6E are cross-sectional views each illustrating a method for manufacturing a semiconductor device according to a second variation of the first preferred embodiment.

FIG. 7 is a top view illustrating a structure of a semiconductor device according to a second preferred embodiment;

FIG. 8 is a cross-sectional view taken along line B-B of FIG. 7;

FIG. 9 is a diagram, of a variation of the second preferred embodiment, equivalent to FIG. 8; and

FIGS. 10A to 10D are cross-sectional views each illustrating a method for manufacturing a semiconductor device according to the variation of the second preferred embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Preferred Embodiment

<Structure of Semiconductor Device>

A first preferred embodiment will be described below with reference to the drawings. FIG. 1 is a top view illustrating a structure of a semiconductor device according to the first preferred embodiment. FIG. 2 is a cross-sectional view taken along line A-A of FIG. 1

As illustrated in FIGS. 1 and 2, the semiconductor device includes: a metal sheet 1; an insulating pattern 2; a plurality of power circuit patterns 3 a; a plurality of signal circuit patterns 3 b; a plurality of (for example, six) power semiconductor chips 5 a to 5 f; a plurality of (for example, four) control semiconductor chips 6 a to 6 d; a P electrode 8; a U electrode 9; a V electrode 10; a W electrode 11; an N electrode 12; a plurality of signal terminals 13; a plurality of aluminum wires 14; and a casing 15.

The metal sheet 1 is a member for dissipating heat generated by the power semiconductor chips 5 a to 5 f. The insulating pattern 2 is comprised of ceramic, resin, or the like, and is provided on the entire upper surface of the metal sheet 1. The insulating pattern 2 may be a single component or may be divided into a plurality of pieces. The metal sheet 1 and the insulating pattern 2 may be bonded via solder.

The plurality of power circuit patterns 3 a are provided on a power side (the lower part of FIG. 1) on the upper surface of the insulating pattern 2. The plurality of signal circuit patterns 3 b are provided on a signal side (the upper part of FIG. 1) on the upper surface of the insulating pattern 2. The power circuit patterns 3 a and the signal circuit patterns 3 b correspond to a circuit pattern. When the power circuit patterns 3 a and the signal circuit patterns 3 b are not distinguished from each other, they are simply referred to as a circuit pattern.

The power semiconductor chips 5 a to 5 f are, for example, reverse conducting insulated gate bipolar transistors (RC-IGBTs) in each of which a switching unit and a reflux unit are integrated into one chip, and the power semiconductor chips 5 a to 5 f are mounted on the power circuit patterns 3 a. The power semiconductor chips 5 a to 5 f are bonded to the power circuit patterns 3 a with first die bonding materials 4 a comprised of copper.

Conventionally, solder, which is low in material cost, has been used to bond a power semiconductor chip to a power circuit pattern, but in the present embodiment, in order to improve heat dissipation for the power semiconductor chips 5 a to 5 f, the first die bonding materials 4 a comprised of copper are used.

The power semiconductor chips 5 a to 5 f are also referred to as a first RC-IGBT 5 a to a sixth RC-IGBT 5 f, respectively. In FIG. 1, the power semiconductor chips 5 a to 5 f are shown as the first RC-IGBT 5 a to the sixth RC-IGBT 5 f.

The power semiconductor chips 5 a to 5 f may be each configured with an IGBT chip and a diode which are a separate switching unit and reflux unit.

Further, the metal sheet 1, the insulating pattern 2, and the circuit patterns may be integrally configured as a plastic insulating substrate. In this case, as the circuit pattern of the plastic insulating substrate, it may be possible to employ a copper circuit pattern, which has an excellent contact thermal resistance with respect to the first die bonding materials 4 a comprised of copper.

The control semiconductor chips 6 a to 6 d are semiconductor chips for controlling the power semiconductor chips 5 a to 5 f, and are mounted on the signal circuit patterns 3 b. The control semiconductor chips 6 a to 6 d are bonded to the signal circuit patterns 3 b with the second die bonding materials 4 b. Solder is used as the second die bonding materials 4 b. The control semiconductor chips 6 a to 6 d are also referred to as a first IC chip 6 a to a fourth IC chip 6 d, respectively.

Further, as the second die bonding materials 4 b, it may be possible to use, instead of solder, a die bonding material comprised of copper, a silver die bonding material, or a non-conductive die bonding material such as a silicone adhesive.

The casing 15 is formed so as to surround the side surfaces of the metal sheet 1, the insulating pattern 2, the power circuit patterns 3 a, the signal circuit patterns 3 b, the power semiconductor chips 5 a to 5 f, and the control semiconductor chips 6 a to 6 d.

The P electrode 8, the U electrode 9, the V electrode 10, the W electrode 11, and the N electrode 12 are provided on the power side of the casing 15, and are connected to the power circuit patterns 3 a with the aluminum wires 14. Further, the signal terminals 13 are provided on the signal side of the casing 15, and are connected to the signal circuit patterns 3 b with the aluminum wires 14.

Next, a circuit configuration of the semiconductor device will be described with reference to FIG. 3 FIG. 3 is a circuit diagram of the semiconductor device according to the first preferred embodiment. In FIG. 3, the control semiconductor chips 6 a to 6 d are respectively shown as the first IC chips 6 a to the fourth IC chips 6 d.

As illustrated in FIG. 3, in order to drive the power semiconductor chips 5 a to 5 f, which have different output phases and different functions as upper arms or lower arms, the control semiconductor chips 6 a to 6 d are respectively provided so as to make pairs with the phases. However, because the control semiconductor chip 6 d has a circuit configuration to drive the power semiconductor chips 5 d to 5 f, the control semiconductor chip 6 d is integrated into one chip.

The control semiconductor chip 6 d may be configured with three control semiconductor chips so as to individually drive the power semiconductor chips 5 d to 5 f.

<Method for Manufacturing Semiconductor Device>

Next, a method for manufacturing a semiconductor device will be described with reference to FIGS. 4A to 4C. FIGS. 4A to 4C are cross-sectional views each illustrating the method for manufacturing the semiconductor device according to the first preferred embodiment. Note that, in FIGS. 4A to 4C, only the power semiconductor chip 5 b is shown, and the power semiconductor chips 5 a, 5 c to 5 f are not shown. Because these power semiconductor chips are bonded by the same method, the bonding of the semiconductor chips 5 a, 5 c to 5 f are not described in the following description.

First, a metal sheet 1 having the power circuit pattern 3 a and the signal circuit pattern 3 b provided on the insulating pattern 2 is prepared. As illustrated in FIG. 4A, a mask 16 for screen printing is disposed on the power circuit pattern 3 a. At this time, although not illustrated, the mask 16 is disposed also on the signal circuit pattern 3 b. Then, a squeegee 17 is used to pour first paste material 14 a into a portion, of the power circuit pattern 3 a, exposed from the mask 16. Although not illustrated, the second paste material is poured into a portion, of the signal circuit pattern 3 b, exposed from the mask 16.

Next, as illustrated in FIG. 4B, the mask 16 is removed to complete the application of the first paste material 14 a and the application of the second paste material (not shown).

At this point in the method, the first paste material 14 a is in a state of the first die bonding material 4 a before curing, and the first paste material 14 a is specifically a copper paste material. The second paste material is in a state of the second die bonding material 4 b before curing, and the second past material is specifically a solder paste material.

Next, the power semiconductor chip Sb is mounted on the first paste material 14 a. Although not illustrated, the control semiconductor chips 6 a to 6 d are mounted on the second paste materials. Then, a heat treatment is performed to cure the first paste material 14 a, so that the first die bonding material 4 a is formed as illustrated in FIG. 4C, whereby the power semiconductor chip Sb is bonded to the power circuit pattern 3 a with the first die bonding material 4 a. Although not illustrated, the above heat treatment cures the second paste materials to form the second die bonding materials 4 b, and the control semiconductor chips 6 a to 6 d are bonded to the signal circuit patterns 3 b with the second die bonding materials 4 b.

In the above, the first paste material 14 a and the second paste materials 14 b are subjected to a heat treatment in the same step. However, since the first paste material 14 a is a copper paste material and the second paste material 14 b is a solder paste material, the curing temperature of the second paste material 14 b is lower than the curing temperature of the first paste material 14 a. Therefore, the first paste material 14 a and the second paste material 14 b may be subjected to a heat treatment in different steps.

FIGS. 5A to 5F are cross-sectional views each illustrating a method for manufacturing a semiconductor device according to a first variation of the first preferred embodiment. Note that, in FIGS. 5A to 5F, only the power semiconductor chip 5 b and the control semiconductor chip 6 b are shown, and the power semiconductor chips 5 a, 5 c to 5 f and the control semiconductor chips 6 a, 6 c, 6 d are not shown. However, because the power semiconductor chips 5 a to 5 f are bonded by the same method and the control semiconductor chips 6 a to 6 d are bonded by the same method, a description is not given on the bonding of the power semiconductor chips 5 a, 5 c to 5 f or the control semiconductor chips 6 a, 6 c, 6 d.

As illustrated in FIG. 5A, a mask 16 for screen printing is disposed on the circuit pattern. Then, a squeegee 17 is used to pour second paste material 14 b into a portion, of the signal circuit pattern 3 b, exposed from the mask 16.

Next, as illustrated in FIG. 5B, the mask 16 is removed to complete the application of the second paste material 14 b.

Next, the control semiconductor chip 6 b is mounted on the second paste material 14 b. Then, a heat treatment is performed at a temperature lower than the temperature for the first paste material 14 a, and the second paste material 14 b is cured to form the second die bonding material 4 b as illustrated in FIG. 5C, so that the control semiconductor chip 6 b is bonded to the signal circuit pattern 3 b with the second die bonding material 4 b.

Next, as illustrated in FIG. 5D, a mask 16 for screen printing is disposed on the circuit pattern. At this time, the mask 16 is dispose so as to cover the control semiconductor chip 6 b. Then, a squeegee 17 is used to pour first paste material 14 a into a portion, of the power circuit pattern 3 a, exposed from the mask 16.

Next, as illustrated in FIG. 5E, the mask 16 is removed to complete the application of the first paste material 14 a.

Next, the power semiconductor chip 5 b is mounted on the first paste material 14 a. Then, a heat treatment is performed at a temperature higher than the temperature for the second paste material 14 b, and the first paste material 14 a is cured to form the first die bonding material 4 a as illustrated in FIG. 5F, so that the power semiconductor chip 5 b is bonded to the power circuit pattern 3 a with the first die bonding material 4 a.

In the above two manufacturing methods, the first paste material 14 a is applied to have a flat upper surface. However, when the power semiconductor chip 5 b is mounted on the first paste material 14 a, the power semiconductor chip 5 b is pushed into the first paste material 14 a, so that the first paste material 14 a creeps up in some cases. To prevent or reduce the creep up, the first paste material 14 a may be shaped. FIGS. 6A to 6E are cross-sectional views each illustrating a method for manufacturing a semiconductor device according to a second variation of the first preferred embodiment.

Note that, in FIGS. 6A to 6E, only the power semiconductor chip 5 b is shown, and the power semiconductor chips 5 a, 5 c to 5 f are not shown. Because these power semiconductor chips are bonded by the same method, the bonding of the semiconductor chips 5 a, 5 c to 5 f are not described in the following description. Further, since the control semiconductor chips 6 a to 6 d are bonded by the same method as in the case of FIGS. 4A to 4C, and a description will not be given on the control semiconductor chips 6 a to 6 d.

As illustrated in FIG. 6A, a mask 16 for screen printing is disposed on the power circuit pattern 3 a. Then, a squeegee 17 is used to pour first paste material 14 a into a portion, of the power circuit pattern 3 a, exposed from the mask 16.

Next, as illustrated in FIG. 6B, the mask 16 is removed to complete the application of the first paste material 14 a.

Next, as illustrated in FIG. 6C, a mask 18 for shaping is disposed on the first paste material 14 a applied on the power circuit pattern 3 a. A top view contour of the mask 18 is formed to have the same size as a top view contour of the first paste material 14 a applied on the power circuit pattern 3 a. In a part, of the lower surface of the mask 18, other than the outer peripheral part, in other words, an inner peripheral part of the lower surface of the mask 18, there is formed a recessed portion 18 a that is recessed upward. The recessed portion 18 a is disposed on the first paste material 14 a, so that the first paste material 14 a is shaped. When the mask 18 is removed, as illustrated in FIG. 6D, the part, of the first paste material 14 a, other than the outer peripheral part, in other words, the inner peripheral part of the first paste material 14 a is shaped to protrude upward.

Next, the power semiconductor chip 5 b is mounted on the first paste material 14 a. At this time, although not illustrated, the power semiconductor chip Sb is pushed onto the portion, of the first paste material 14 a, protruding upward. Regarding the first paste material 14 a, the outer peripheral part on the outer part of the upwardly protruding portion is recessed downward; therefore, the entire upper surface of the first paste material 14 a becomes flat when the power semiconductor chip Sb is pushed in. As a result, the creeping up of the first paste material 14 a can be prevented or reduced.

Next, a heat treatment is performed to cure the first paste material 14 a, so that the first die bonding material 4 a is formed as illustrated in FIG. 6E, whereby the power semiconductor chip 5 b is bonded to the power circuit pattern 3 a with the first die bonding material 4 a.

The shaping of the first paste material 14 a in the second variation of the first preferred embodiment may be employed in the first variation of the first preferred embodiment.

Advantageous Effects

As described above, the semiconductor device according to the first preferred embodiment includes: the metal sheet 1; the insulating pattern 2 provided on the metal sheet 1; the power circuit patterns 3 a and the signal circuit patterns 3 b that are provided on the insulating pattern 2; the power semiconductor chips 5 a to 5 f mounted on the power circuit patterns 3 a; and the control semiconductor chips 6 a to 6 d that are mounted on the signal circuit patterns 3 b and control the power semiconductor chips 5 a to 5 f. The power semiconductor chips 5 a to 5 f are bonded to the power circuit patterns 3 a with first die bonding materials 4 a comprised of copper, and the control semiconductor chips 6 a to 6 d are bonded to the signal circuit patterns 3 b with second die bonding materials 4 b.

As a result, since the first die bonding materials 4 a comprised of copper are used to bond the power semiconductor chips 5 a to 5 f and the power circuit patterns 3 a, heat dissipation for the power semiconductor chips 5 a to 5 f is improved as compared with a conventional case where solder is used. Therefore, the heat dissipation for the power semiconductor chips 5 a to 5 f can be ensured even when the power circuit patterns 3 a are thinned. As a result, it is possible to secure the heat dissipation for the power semiconductor chips 5 a to 5 f and to achieve miniaturization of the semiconductor device.

The metal sheet 1, the insulating pattern 2, the power circuit patterns 3 a, and the signal circuit patterns 3 b are integrally configured.

In the case where the insulating pattern 2 is configured of ceramic, since the ceramic is a brittle material that is vulnerable to displacement, the insulating pattern 2 is divided into a plurality of parts, in some cases, in order to prevent or reduce influence due to deformation of the metal sheet 1 when the semiconductor device is driven. In the case of a plastic insulating substrate in which the metal sheet 1, the insulating pattern 2, the power circuit patterns 3 a, and the signal circuit patterns 3 b are integrally configured, it is possible to prevent or reduce the influence due to the deformation of the metal sheet 1 even if the insulating pattern is not divided into a plurality of parts. Therefore, a degree of freedom in layout design of the semiconductor device is improved, and it is possible to achieve further miniaturization of the semiconductor device.

Further, the method for manufacturing the semiconductor device according to the first preferred embodiment includes: a step (a) of applying the first paste materials 14 a, which are in a state of the first die bonding materials 4 a before curing, on the power circuit patterns 3 a and applying the second paste materials 14 b, which are in a state of the second die bonding materials 4 b before curing, on the signal circuit patterns 3 b; a step (b) of mounting the power semiconductor chips 5 a to 5 f on the first paste materials 14 a and mounting the control semiconductor chips 6 a to 6 d on the second paste materials 14 b; and a step (c) of curing the first paste materials 14 a and the second paste materials 14 b.

Therefore, by performing screen printing, it is possible to collectively apply the first paste materials 14 a to the power semiconductor chips 5 a to 5 f of various phases, so that the productivity of the semiconductor device can be improved.

Further, the method for manufacturing the semiconductor device according to the first variation of the first preferred embodiment includes: a step (h) of applying the second paste materials 14 b, which are in a state of the second die bonding materials 4 b before curing, on the signal circuit patterns 3 b, a step (i) of mounting the control semiconductor chips 6 a to 6 d on the second paste materials 14 b, a step (j) of curing the second paste materials 14 b; a step (k) of applying the first paste materials 14 a, which are in a state of the first die bonding materials 4 a before curing, on the power circuit patterns 3 a; and a step (1) of mounting the power semiconductor chips 5 a to 5 f on the first paste materials 14 a; and a step (m) of curing the first paste materials 14 a. The curing temperature of the second paste materials 14 b is lower than the curing temperature of the first paste materials 14 a.

Therefore, a curing time of the second paste materials 14 b can be shorter than a curing time of the first paste materials 14 a, so that the productivity of the semiconductor device can be improved.

Further, the method for manufacturing the semiconductor device according to the second variation of the first preferred embodiment further includes, between the step (a) and the step (b) or between the step (k) and the step (1), a step (n) of shaping the first paste materials 14 a such that the outer peripheral parts of the first paste materials 14 a are recessed downward with respect to the inner peripheral parts of the first paste materials 14 a.

When the power semiconductor chips 5 a to 5 f are mounted on the first paste materials 14 a, the power semiconductor chips 5 a to 5 f are pushed onto the portions, of the first paste materials 14 a, protruding upward. Regarding each first paste materials 14 a, the outer peripheral part on the outer side of the upwardly protruding portion is recessed downward; therefore, the entire upper surface of the first paste material 14 a becomes flat. As a result, the creeping up of the first paste materials 14 a can be prevented or reduced.

Second Preferred Embodiment

<Structure of Semiconductor Device>

Next, a semiconductor device according to a second preferred embodiment will be described. FIG. 7 is a top view illustrating a structure of the semiconductor device according to the second preferred embodiment. FIG. 8 is a cross-sectional view taken along line B-B of FIG. 7. In the second preferred embodiment, the same components as those described in the first preferred embodiment are assigned the same reference signs, and the description thereof will be omitted.

As illustrated in FIGS. 7 and 8, in the second preferred embodiment, the semiconductor device further includes capacitive components 7 a to 7 d mounted on signal circuit patterns 3 b. The capacitive components 7 a to 7 d are, for example, capacitors.

The capacitive components 7 a to 7 d are each bonded to two signal circuit patterns 3 b with third die bonding materials 4 c comprised of copper, and are respectively arranged so as to make pairs with control semiconductor chips 6 a to 6 d. Here, the thickness of the third die bonding materials 4 c is the same as the thickness of the first die bonding materials 4 a. Further, the capacitive components 7 a to 7 d are electrically connected to the power semiconductor chips 5 a to 5 f with aluminum wires 14.

By providing the capacitive components 7 a to 7 d, it is possible to supply stable voltages from the capacitive components 7 a to 7 d to the power semiconductor chips 5 a to 5 f when a voltage drop occurs when the semiconductor device is driven.

It is also possible to make the thickness of the first die bonding materials 4 a thicker than the thickness of the third die bonding materials 4 c. FIG. 9 is a diagram, of a variation of the second preferred embodiment, equivalent to FIG. 8.

As illustrated in FIG. 9, by increasing the thickness of the first die bonding material 4 a directly under the power semiconductor chip 5 b, it is possible to further improve the heat dissipation of the semiconductor device.

<Method for Manufacturing Semiconductor Device>

Next, a method for manufacturing the semiconductor device will be described. As illustrated in FIG. 8, when the thickness of the third die bonding material 4 c is the same as the thickness of the first die bonding material 4 a, the same steps as for the power semiconductor chips 5 a to 5 f illustrated in FIGS. 4A to 4C are performed as follows: a third paste material, which is in a state of the third die bonding material 4 c before curing, is applied; the capacitive components 7 a to 7 d are mounted; and then, the third paste material 14 c is cured. Therefore, the case of FIG. 8 will not be described.

Hereinafter, with reference to FIGS. 10A to 10D, a description will be given on a method for manufacturing the semiconductor device according to a variation of the second preferred embodiment illustrated in FIG. 9. FIGS. 10A to 10D are cross-sectional views each illustrating the method for manufacturing the semiconductor device according to the variation of the second preferred embodiment.

Note that, in FIGS. 10A to 10D, only the power semiconductor chip Sb and the capacitive component 7 b are shown, and the power semiconductor chips 5 a, Sc to 5 f and the capacitive components 7 a, 7 c, 7 d are not shown. However, because the power semiconductor chips 5 a to 5 f are bonded by the same method and the capacitive components 7 a to 7 d are bonded by the same method, a description is not given on the bonding of the power semiconductor chips 5 a, 5 c to 5 f or the bonding of the capacitive components 7 a, 7 c, 7 d.

As illustrated in FIG. 10A, a mask 16 for screen printing is disposed on the circuit pattern. Then, by using a squeegee 17, the third paste materials 14 c are poured into portions of the signal circuit pattern 3 b which are exposed from the mask 16 and on which the capacitive component 7 b is mounted. Although not illustrated, the second paste materials are poured into portions of the signal circuit patterns 3 b which are exposed from the mask 16 and on which the control semiconductor chips 6 a to 6 d are mounted. Then, the mask 16 is removed to complete the application of the third paste materials 14 c and the application of the second paste materials (not shown).

Next, as illustrated in FIG. 10B, a mask 16 a for screen printing, which is thicker than the mask 16, is disposed on the circuit pattern. Then, a squeegee 17 is used to pour first paste material 14 a into a portion, of the power circuit pattern 3 a, exposed from the mask 16 a. Then, the mask 16 a is removed to complete the application of the first paste material 14 a.

Next, as illustrated in FIG. 10C, the power semiconductor chip 5 b is mounted on the first paste material 14 a, and the capacitive component 7 b is mounted on the third paste materials 14 c. Although not illustrated, the control semiconductor chips 6 a to 6 d are mounted on the second paste materials.

Then, a heat treatment is performed to cure the first paste material 14 a and the third paste material 14 c, so that the first die bonding material 4 a and the third die bonding materials 4 c are formed as illustrated in FIG. 10D. As a result, the power semiconductor chip 5 b is bonded to the power circuit pattern 3 a with the first die bonding material 4 a, and the capacitive component 7 b is bonded to the signal circuit patterns 3 b with the third die bonding materials 4 c. Although not illustrated, the above heat treatment cures the second paste materials to form the second die bonding materials 4 b, and the control semiconductor chips 6 a to 6 d are bonded to the signal circuit patterns 3 b with the second die bonding materials 4 b.

Advantageous Effects

As described above, the semiconductor device according to the second preferred embodiment further includes the capacitive components 7 a to 7 d mounted on the signal circuit patterns 3 b and electrically connected to the power semiconductor chips 5 a to 5 f. The capacitive components 7 a to 7 d are bonded to the signal circuit patterns 3 b with the third die bonding materials 4 c comprised of copper.

With this arrangement, it is possible to supply stable voltages from the capacitive components 7 a to 7 d to the power semiconductor chips 5 a to 5 f when a voltage drop occurs when the semiconductor device is driven. This makes it possible to improve reliability of the semiconductor device.

Further, since the thickness of the first die bonding materials 4 a is thicker than the thickness of the third die bonding material 4 c, it is possible to improve the heat dissipation of the semiconductor device. At this time, the signal circuit patterns 3 b directly under the capacitive components 7 a to 7 d can be made fine, which contributes to miniaturization of the semiconductor device.

Further, the method for manufacturing the semiconductor device according to the variation of the second preferred embodiment includes: a step (d) of applying, on the signal circuit patterns 3 b, the second paste materials 14 b, which are in a state of the second die bonding materials 4 b before curing and the third paste materials 14 c, which are in a state of the third die bonding materials 4 c before curing, such that both paste materials are thinner than the thickness of the first paste materials 14 a, which are in a state of the first die bonding materials 4 a before curing; a step (e) of applying the first paste materials 14 a on the power circuit patterns 3 a; a step (f) of mounting the power semiconductor chips 5 a to 5 f on the first paste materials 14 a, mounting the control semiconductor chips 6 a to 6 d on the second paste materials 14 b, and mounting the capacitive components 7 a to 7 d on the third paste materials 14 c; and a step (g) of curing the first paste materials 14 a, the second paste materials 14 b, and the third paste materials 14 c.

Therefore, by separately performing two screen printing steps, the paste materials having different thicknesses can be applied; therefore, it is possible to easily manufacture a semiconductor device having improved heat dissipation.

The shaping of the first paste materials 14 a in the second variation of the first preferred embodiment may be employed in the second preferred embodiment and its variation. Specifically, the method further includes, between the step (e) and the step (f), a step (n) of shaping the first paste materials 14 a such that the outer peripheral parts of the first paste materials 14 a are recessed downward with respect to the inner peripheral parts of the first paste materials 14 a. As a result, it is possible to prevent or reduce creeping up of the first paste materials 14 a.

In addition, the preferred embodiments can be arbitrarily combined, and each preferred embodiment can be appropriately modified or omitted.

While the disclosure has been shown and described in detail, the foregoing description is in all aspects illustrative and not restrictive. It is therefore understood that numerous modifications and variations can be devised. 

What is claimed is:
 1. A semiconductor device comprising: a metal sheet; an insulating pattern provided on the metal sheet; a circuit pattern provided on the insulating pattern; a power semiconductor chip mounted on the circuit pattern; and a control semiconductor chip that is mounted on the circuit pattern and controls the power semiconductor chip, wherein the power semiconductor chip is bonded to the circuit pattern with a first die bonding material comprised of copper, and the control semiconductor chip is bonded to the circuit pattern with a second die bonding material.
 2. The semiconductor device according to claim 1, further comprising a capacitive component mounted on the circuit pattern and electrically connected to the power semiconductor chip, wherein the capacitive component is bonded to the circuit pattern with a third die bonding material comprised of copper.
 3. The semiconductor device according to claim 1, wherein the metal sheet, the insulating pattern, and the circuit pattern are integrally configured.
 4. The semiconductor device according to claim 2, wherein the first die bonding material has a thickness thicker than a thickness of the third die bonding material.
 5. A method for manufacturing a semiconductor device that is for manufacturing the semiconductor device according to claim 1, the method comprising: (a) applying, on the circuit pattern, a first paste material, which is in a state of the first die bonding material before curing, and a second paste material, which is in a state of the second die bonding material before curing; (b) mounting the power semiconductor chip on the first paste material and the control semiconductor chip on the second paste material; and (c) curing the first paste material and the second paste material.
 6. A method for manufacturing a semiconductor device that is for manufacturing the semiconductor device according to claim 2, the method comprising: (d) applying, on the circuit pattern, a second paste material, which is in a state of the second die bonding material before curing and a third paste material, which is in a state of the third die bonding material before curing, wherein the second paste material and the third paste material are applied thinner than a thickness of a first paste material, which is in a state of the first die bonding material before curing; (e) applying the first paste material on the circuit pattern; (f) mounting the power semiconductor chip on the first paste material, the control semiconductor chip on the second paste material, and the capacitive component on the third paste material; and (g) curing the first paste material, the second paste material, and the third paste material.
 7. A method for manufacturing a semiconductor device that is for manufacturing the semiconductor device according to claim 1, the method comprising: (h) applying, on the circuit pattern, a second paste material, which is in a state of the second die bonding material before curing; (i) mounting the control semiconductor chip on the second paste material; (j) curing the second paste material; (k) applying, on the circuit pattern, a first paste material, which is in a state of the first die bonding material before curing; (l) mounting the power semiconductor chip on the first paste material; and (m) curing the first paste material, wherein a curing temperature of the second paste material is lower than a curing temperature of the first paste material.
 8. The method for manufacturing a semiconductor device according to claim 5, further comprising, between the step (a) and the step (b), (n) shaping the first paste material such that an outer peripheral part of the first paste material is recessed downward with respect to an inner peripheral part of the first paste material.
 9. The method for manufacturing a semiconductor device according to claim 6, further comprising, between the step (e) and the step (f), (n) shaping the first paste material such that an outer peripheral part of the first paste material is recessed downward with respect to an inner peripheral part of the first paste material.
 10. The method for manufacturing a semiconductor device according to claim 7, further comprising, between the step (k) and the step (1), (n) shaping the first paste material such that an outer peripheral part of the first paste material is recessed downward with respect to an inner peripheral part of the first paste material. 